Protein phosphatase PPM1B, also named as PP2Cβ, is a member of serine/threonine phosphatase family. Dysregulated expression of PPM1B has been reported in several malignancies; nevertheless, its role in gastric cancer remains unknown. Here, we aimed to initially investigate the expression and function of PPM1B in gastric adenocarcinoma.We firstly evaluated the protein expression of PPM1B in our enrolled retrospective cohort (n=161) via immunohistochemistry staining. Univariate and multivariate analyses were conducted to assess its prognostic value. Cellular experiments and xenografts in mice model were also performed to validate the role of PPM1B in gastric adenocarcinoma progression.The advanced tumor stage was characterized with a lower PPM1B level. Lower PPM1B was associated with poor prognosis in both The Cancer Genome Atlas (TCGA) dataset and our cohort (P<0.05). Furthermore, Cox regression analysis demonstrated that PPM1B was a novel independent prognostic factor for gastric adenocarcinoma patients (hazard ratio=0.35, P=0.001). Finally, cellular and xenografts data confirmed that overexpressing PPM1B can remarkably attenuated gastric adenocarcinoma growth.Low expression of PPM1B may be a potential molecular marker for poor prognosis in gastric adenocarcinoma.Copyright © 2022 Wolters Kluwer Health, Inc. All rights reserved.